My house is served by mini (9"?) inspection chambers. The pics show (I hope) two of them. I'd like to raise the level of the lower one, to incorporate it into an extended patio coming out from the back door. (The step is a bit steep, and we are getting older and clumsier!) The haunching shows the height increase needed. Any ideas? I'm assuming that 'kits' are not available!
Cheers.
Cheers.